Process for purifying impure diphenols

Abstract

A process for improving the quality of diphenols by recrystallization from aqueous solvent systems.

What is claimed is: 
     
       1. A process for purifying impure p,p' -diphenols which comprises dispersing the impure diphenol in water, heating the resulting slurry, adding a water soluble polar, aprotic co-solvent until the dissolution or near dissolution of the diphenol slurry results at or near the boiling point of water or the solvent system, cooling the solution to achieve the separation of the purified diphenol and recovering the purified p,p' -diphenol. 
     
     
       2. A process according to claim 1 wherein the polar, aprotic co-solvent is selected from the group consisting of amides, sulfoxides, sulfones, phosphoramides, sulfamides, nitriles and ethers. 
     
     
       3. A process according to claim 2 wherein the co-solvent is selected from the group consisting of dimethylformamide, dimethylsulfoxide, N-methylpyrrolidene and acetonitrile. 
     
     
       4. A process according to claim 1 wherein the impure diphenol is 2,2'-bis(4-hydroxyphenyl)propane. 
     
     
       5. A process according to claim 1 wherein the dissolution or near dissolution of the diphenol slurry results at about 90° to 100° C at atmospheric pressure. 
     
     
       6. A process according to claim 1 wherein the dissolution or near dissolution of the diphenol slurry is carried out at super-amtospheric pressure. 
     
     
       7. A process for purifying impure p,p' -diphenols which comprises dispersing the impure diphenol in a mixture of water and a water soluble polar, aprotic co-solvent or mixtures of co-solvents, heating the resultant slurry until the dissolution or near dissolution is achieved, cooling the solution to achieve the separation of the purified diphenol and recovering the purified p,p' -diphenol. 
     
     
       8. A process according to claim 7 wherein the polar, aprotic co-solvent is selected from the group consisting of amides, sulfoxides, sulfones, phosphoramides, sulfamides, nitriles and ethers. 
     
     
       9. A process according to claim 8 wherein the co-solvent is selected from the group consisting of dimethylformamide, dimethylsulfoxide, N-methylpyrrolidene and acetonitrile. 
     
     
       10. A process according to claim 7 wherein the impure diphenol is crude 2,2'-bis(4-hydroxyphenyl)propane. 
     
     
       11. A process according to claim 7 wherein the dissolution or near dissolution of the diphenol slurry results at about 90° to 100° C at atmospheric pressure. 
     
     
       12. A process according to claim 7 wherein the dissolution or near dissolution of the diphenol slurry is carried out at super-atmospheric pressure.